Tarp fabric resistant to hail and extreme weather

The links to more than one video shot in the field during hail storms that created massive holes in 0.51 DCF were on a thread over at the ultralight reddit.

I just did a quick search but couldn’t find the videos that I saw before. But here’s a photo that communicates the same thing:

What happened to the replies to my post from Justin, Jerry, and Greg?

Jerry: Yes, I think the mid design would be ideal. RSBTR’s MTN silnylon sounds awesome but they don’t have any colors in stock except white. Extrem Textil in Germany has a selection of silnylons that are the same as some of those used by Hilleberg, I think.

Justin: Yes, nylon would definitely be better because of the inherent stretch.

I’ve used 0.51 DCF in hail storms a number of times and it hasn’t failed but it doesn’t surprise me that it could. Given the frequency with which I encounter big hail storms in the Pyrenees, I think it would be silly not to take that possibility (of freakishly large hail stones) into account especially when planning for longer trips.

“What happened to the replies to my post from Justin, Jerry, and Greg?”

It seems a (probably small) number of posts have gone missing after the update today.

Hilleberg use 40D nylon 6.6 for the Black Labels, 30D for Red Labels like the Akto, and 20D for the Yellow Labels, which they define as ” less than ideal for fully exposed or high altitude terrain or remote adventures”. But I suspect they’re being conservative to protect their reputation and allowing for unskilled users.

Given that the Hille fabrics are as good as you can get, my own feeling is that anything under 20D would be seriously pushing it in exposed terrain.

A good 20D is probably OK for 3+ season conditions provided the shelter is well designed. MLD supply the TrailStar in 20D silnylon, and that’s not exactly a wimpy shelter.

While 30D gives you a generous safety margin – the Akto has been used for some pretty hairy Arctic expeditions and came through OK.

As for DCF, in the past Ron Bell at MLD would only supply the 0.5 at the owner’s risk, but his current Fabric Mojo has softened a bit and he’s now prepared to recommend it for 3.5 season use, though he warns of shorter life. Personally, in areas with risk of hail or big winds I’d prefer to go up a weight and reduce the risk of very expensive damage…

“Planned Maintenance/Outage: Website Updates Today”

Probably explains where Justin and my posts went, not to worry : )

Justin said maybe 20D 6,6 nylon would be good, I posted that RSBTR has 30D 1.1 oz/yd2 6,6 MTN silnylon and mid design is good because of steep angle of fabric causing glancing blow.

Maybe ask them when they might have other colors, or tell them how much you need and they might have something

Extrem Textil carry both the 40D and the 20D silnylon in exactly the same colours used by Hilleberg. The quality of the fabrics carried by Extrem Textil is quite high. I recently got to see some of the 7D downproof fabric in person and was really impressed by it. Hence my strong suspicion that the 40D and 20D silnylons they carry are the same as those used by Hille.

I’m less worried about damage that is expensive rather than situations that pose a risk to health and life. I’d hate to be camped up at 2500+ meters and go through a hail storm in the middle of the night lasting hours only to discover that my shelter was no longer one. I think my body’s ability to fight off exposure and hypothermia isn’t as robust as it used to be and in any case lots of people stronger than me have died on the mountain from those causes.

I’m willing to carry 200 grams extra weight for the security on certain trips.

I had an Akto for a number of years, one of the earlier models with the more robust fabric. Had it through some vicious gale force winds and it performed like a champ. It was too heavy, though.

If I were going in that direction today, I’d be much more tempted by the Aarn 1 used with trekking poles. It’s a tunnel design that uses a 30D 6.6 silnylon and has inner stabilizer guys, a ridiculous number of tie outs for external guys, and reportedly weighs 1.33 kg.

In addition to Jerry’s post that went missing here are two more:

Greg Mihalik wrote:

“We’ve all seen the videos of 0.51 DCF failing in hail storms.”

I haven’t.  Got a link?

Justin W wrote:

I wouldn’t trust any of the ultralight materials with truly extreme conditions–especially not DCF or silpoly.

Silnylon is more forgiving because it stretches more before it breaks, plus it has greater tenacity at less weight than silpoly. It can absorb more energy for things like hail.

I don’t know if they make it or not, but I might feel ok with a 20D silnylon (especially if made out of a 6.6 type nylon).  I made a 10D silnylon tarp for my spouse for a trip awhile back, and I don’t know if I would trust that with extreme conditions.

But, at the same time, I’m more a fan of testing rather than just presupposing. Just would do the testing at home or near civilization and not out on a longer or more remote type trip.

So the Aarn 1 Mk2 is out at last – it’s been delayed for so long I’d given up checking!

As per usual with Aarn, not enough info to make much of a judgement – not a single photo of the inner, for example.

Given it’s designed for the NZ Alps I think we can take it that it’s bomber, and at only 0.7kg without the inner and 1.3kg with trekking pole support it’s a decent weight.

But I think it might be coffin-like. Especially with the inner, there’s going to be very little space above your head and feet.

As you say – 30D 6.6 for the fly, and a 70D floor. Same spec as the Akto, but almost half a kilo lighter if you use trekking poles. So quite a tough beastie for the weight…

Yeah, not a very convincing website presentation, I agree

The dimensions look generous to me Geoff. At 3.6 meters in length, the outer tent is much longer than the Akto. It looks like that means that the head and foot ends of the inner are high enough to avoid a face full of ripstop. The length of the outer probably allows for storage in the ends, too. The width of the inner looks fine.

I have shopped Tarptent lots. Years ago they upgraded to 30 mil silnylon across the board. Their previous fabric was maybe 20 mil (?) silnylon.  It was prone to misting during heavy rain.

I would expect an MLD Grace tarp in their 20D Pro SilNylon to be about as bomber as one is going to get in a UL tarp. That’s not to say there are no others available, but that I think that is the class of shelter needed for the OPs scenario.

“Their previous fabric was maybe 20 mil (?) silnylon.  It was prone to misting during heavy rain.”

That’s more about the coating, tightness and kind of weave involved. Theoretically speaking, you can pack more smaller fibers into a given space than with larger fibers, which would improve HH provided the coating is also high quality.

But the more manufacturers and designers push the envelope with ultralight materials (ever reducing weight and/or fiber size)–the more they might need to start thinking about double layers, rather than one single layer.

Reason being is that you get a greater HH that is non linear in nature, than just adding up the combined HH of two fabrics.   That’s because the outermost layer, absorbs the majority of the force/energy of the falling rain drops, and the layer below is subjected to more static conditions.  Granted, this works best if there is at least a tiny amount of space between them.

So, in other words, having two layers of ultralight fabrics, which each respectively having say only an HH of 1200mm each (say these are both 10 or 7D silnylon)–the HH will be more than sum of 2400mm.  It may actually exceed a high quality, highly waterproof single layer of fabric with say a HH of 3500mm.

This is the driving principle behind why 3 and 2.5 layers of WPB materials can and often do have much higher HH levels than single layer fabrics, even though one or two layers has a fairly porous structure (the breathable part).

It’s all about absorbing and deflecting that initial velocity/force/energy of the rain with the first layer.

It’s also how Paramo, Buffalo, US military, etc type systems get away with using such porous, and individually non waterproof materials (though, there are some other key differences with these systems, and generally these kind also rely on using the heat of the body to drive out moisture).

Justin – interesting concept, but I can’t see how it would apply to a shelter. A couple of layers of 10 d would be light enough, but I suspect they would flap against each other and you’d get fungus build-up between the layers.

Any ideas?

that makes sense that tw0 are better than the sum of the parts

maybe glue the two layers together with silicone?  maybe that would lose some of the advantage?

if you have a two layer tent you get that advantage – if there was misting from the top layer, the mist would hit the bottom layer and would be stopped with even a low HH.  You need high HH because raindrops are heavy (relative to mist) hit the tent with high speed, and generate a lot of water pressure pushing through the fabric.

The layers of WPB are more to protect the membrane.  The inner layer protects the membrane from body oils and dirt.  The outer layer protects the membrane from abrasion and water.  (If you have to protect the membrane from water then why the H do you even have a membrane?  If you have a jacket of just the outer DWR layer it isn’t waterproof at all in heavy rain.  Somehow, the combination of DWR and membrane is waterproof.  Except when it isn’t : ) )

“Silnylon is more forgiving because it stretches more before it breaks, plus it has greater tenacity at less weight than silpoly. It can absorb more energy for things like hail.”

I’ll toss in a counter point on this topic. Standardizing for other factors (e.g. weave, denier, coatings etc) the tensile strength of nylon isn’t that different from poly. The conventional wisdom is that nylon is substantially stronger, but that consensus seems to have started from unfair comparisons that pit a silnylon vs a PU poly (where the sil tilts the playing field towards nylon) and thus isn’t nearly as true for silnylon vs silpoly (or even sil versus other PU formulations like PEU).

If you actually dive into the materials literature, you’d be hard pressed to find a source that gives nylon a tensile strength advantage greater than 20%, which is a far cry from many of the numbers tossed around casually on the internet. The best info seems to put them as very similar. For example, DuPont actually makes these fibers as when they compare the best nylon (nylon 6,6) to poly they give nylon a 1% advantage in mass specific tensile strength (source, see table II-2).

So nylon has an advantage somewhere in the range of 1-20%, which sounds desirable except nylon has two big disadvantages. First, it’s hydrophilic so it absorbs water and expands, which weakens the material by roughly 10% as the molecules move further apart (in addition to other disadvantages like a saggy pitch, becoming heavy, and slow drying). So right off the bat, the 1-20% advantage that nylon has is largely negated in a storm as the fabric weakens. Secondly, nylon is highly susceptible to UV degradation and especially so for these lightweight versions. A new nylon tent can lose 5-10% tensile strength in a single day of being pitched in the sun, and it’s common for nylon tents that are a few years old to be 50% or less of their original tensile strength. Conversely, polyester is largely immune to UV degradation. Thus, nylon and poly start off about the same but in the long run polyester is much stronger.

As for stretch, that’s a highly debatable topic since it’s true that stretch helps absorb energy, and buffer and even out forces. But the flip side is that as it stretches it can become worse at shedding wind (as it “scoops”). And certainly there is a notably loss in snow shedding. Nylon can catch a lot of wind due to the stretch plus sag in wet conditions that  makes it wrinkly, which is why companies like TarpTent tout the non-stretch of DCF as being better in storms. There’s pros and cons either way. I don’t have a clear opinion onit myself, but poly is in the middle where it doesn’t have much stretch in the fibers but still has a moderate amount in the weave.

interesting, that all makes sense, good info, thanks

I’ve been using 0.93 oz/yd2 silpoly tent for a while and it has withstood winds very well.  I don’t regret switching from silnylon.  It seems plenty strong.

I thought nylon was more stronger than polyester than that

The silpoly does stretch quite a bit, similar to nylon, but it’s advantage is it doesn’t change when it gets wet or cold.  The “break elongation” from your table shows nylon a little worse, I think that’s how much it stretches.  As you pitch your tent, if the nylon stretches a little more, it’s not that important.  Maybe the tent designer has to take this into account, but it’s a small effect.

silnylon – I pitch tent taut in the evening, the next morning it’s loose hanging in my face inside.  Silpoly is better.

I’ve tested a piece of silnylon in the full sun for one year.  It didn’t seem significantly UV degraded.  It ripped about the same, probably a little worse than new.  I think UV degradation isn’t so important for a tent that you set up each day.  If you left a tent in the sun for one summer, UV degradation not that big a deal.  If you have a patio or boat cover that you want to last for years, don’t use nylon, it will get UV degraded.

Jon,

One thing to consider about those ExtremTextil silnylons: if they are the same fabrics as used by Hille they may stretch a lot with moisture. Others, including yourself may know more, but I once saw a Keron 3 tunnel, set up nice and taut, sag more than any shelter I’ve ever seen as dusk fell. No rain, only a slight drop in summertime temps, presumably to the dewpoint, and the thing transformed into a sharpei puppy. My wife said “I don’t want a silnylon shelter.”

But we did get a silnylon shelter – a cheap 20d silnylon Chinese 8-sided mid by a company in western China known variously as Knot, Glacier Knot, Ice River and Aricxi. I have no explanation for the fact that this cheap 20d stuff sags less than any silnylon I’ve ever seen. We had all night rain several times this summer and in the morning it looked exactly as it did the night before.

You might query Tarptent and MLD about how their silnylons (both upgraded in recent years and 30 and 20d respectively) would fare under hail. I reckon both would be candid about any reports from users that they’ve collected. I think that both their sils sag less than sils of old. RBTR claim their 6,6 Mountain 30d sags very little.

Also could check with Tipik. I know that the gent who runs that company has done a lot of backyard weathering and aging tests of many different fabrics. Not sure if he’s done any hail testing.

There are a lot of formulations of nylon, but the common ones all expand (sag) 2-4%. Nylon 6,6 is at the low end of that, but 2% can still be several inches of slack over the arch of a tent.

Another factor is that coatings slow down how fast nylon can absorb water. I haven’t done enough research on this, but due to coating differences, fabrics that appear to sag less might actually sag the same but take 2 days to get there instead of 2 hrs.

Dan, interesting stuff. But does not help explain the cheap Chinese 20d silnylon I mentioned – it has a very thin coating, or seems to, having a dry crinkly feel rather than the super-slippery and supple hand I associate with high-quality sil. It does seem to absorb a lot of water; it just doesn’t sag.

Dan, BTW, given your findings that poly is not that far behind nylon in tensile strength, do you think 10d silpoly has a place in tent-making? 10d poly should be a little stronger than 7d nylon, by your numbers.

One possibility is that that “cheap Chinese 20d silnylon” is actually silpoly. You could try stretching it parallel to the strands to see if it stretches like nylon. Another clue is if the dye looks a bit pale (poly doesn’t take color as well).

I think 20D is as light as is prudent for the floors of my tents. Could probably go to 15D for the fly and maybe 10D. I think 15D could work with almost no downside, but might require re-doing some reinforcements etc to spread the load more carefully onto the lighter fabric. Then for 10D it’s probably something that could work, but would be entering the realm of more of a “2 season” tent similar to how 7D nylon works for tarps etc but wouldn’t be mistaken for bomber. If I went down that path, I’d probably re-design the whole thing to be less durable and would just acknowledge that compromise and market it more as a 2-season tent. So #3 zippers, maybe one vent instead of 2, maybe singlewall, etc.

I don’t think the Extremtextil offerings are the same as Hilleberg fabrics. They stretch too much and don’t have the crisp feel of nylon 6.6, IMO. Maybe it’s the same factory, which might explain the colors.

I have to counter some of Dan’s counter points. Judging things based on raw fiber strength is reductionist, omitting things like how the fiber bonds with different coatings or how the fiber behaves in woven form. There are simply too many factors in woven coated fabrics that none of us can properly account for individually. Testing actual fabrics is more accurate, but there’s little data on fabrics comparable to what we’re interested in. The best I’ve come across is here https://translate.googleusercontent.com/translate_c?depth=1&hl=en&u=https://www.randonner-leger.org/forum/viewtopic.php%3Fid%3D31744%26p%3D5

Their testing method is crude, but looking at the results (tear strength results in message number #116), it seems that it’s consistent within 10% or so. You can ignore the four rightmost PU coated fabrics if you want to make a more apples to apples comparison. The sample size is too small to say whether nylon or poly fabrics are stronger, but I think it’s fair to say they appear to degrade in strength at very similar rates. Perhaps it’s mostly the silicone coating degrading rather than the actual fabric, and only longer testing would reveal the advantages of poly. But with already 4 months of exposure, that’s somewhat moot

Dan has mentioned that several companies claim nylon being around 20% stronger and losing the advantage after some exposure to sun/moisture in their testing. Maybe this is true for some specific fabrics they tested, but it seems to me this is not true at all for nylon vs poly in general. And to be honest, I wouldn’t be surprised if these numbers were just touted around the industry in a broken telephone manner

Testing actual fabrics is more accurate, but there’s little data on fabrics comparable to what we’re interested in. The best I’ve come across is here https://translate.googleusercontent.com/translate_c?depth=1&hl=en&u=https://www.randonner-leger.org/forum/viewtopic.php%3Fid%3D31744%26p%3D5

That’s an interesting thread, @spiderbro; I spent a lot of time going through it when I was ordering from tipik-tentes. Those tests in the thread are summarised here, and include this useful graph: